Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with agraphical user interface showing our new design.

The outermost broken line rectangle illustrates a display screen orportion thereof and forms no part of the claimed design. The remaininglong dash-long dash and short dash-short dash broken lines illustrateportions of the graphical user interface that form no part of theclaimed design.

CLAIM We claim the ornamental design for a display screen or portionthereof with a graphical user interface, as shown and described.